Composite pianos are known in which an electronic sound source is combined with an acoustic piano. The composite piano can be played both in a normal piano performance mode in which the hammers strike the strings to produce sound, and in an electronic performance mode in which sound is produced by operating the electronic sound source. When such a composite piano is played in the electronic performance mode, the hammer striking sound is prevented by a stop rail that acts as a damper. When the hammer attached to the tip of a hammer shank is about to strike a string, the movement of the hammer shank is checked by the stop rail.
It is essential that the feel of the keys upon operating the keyboard is not influenced by the stoppage of the hammer shanks. For this purpose, the hammer shanks need to be stopped just prior to striking the strings. Therefore, the stop rail is preferably wide enough to stop the hammer shank abruptly and firmly.
In the conventional damper, as shown in FIG. 8, a stop rail 84 is supported on a support 82 such that the rail 84 is rotatable in the direction shown by an arrow. In the electronic performance mode the stop rail 84 is rotated to the stop position shown by a solid line, where the contact face, defined by a cushioning member 85 attached to the stop rail 84, contacts and stops the hammer shanks 86. In the normal piano performance mode, the stop rail 84 is rotated to the retracted position, shown by a dotted line, that is substantially perpendicular to the stop position. When the stop rail 84 is in the retracted position, the hammers 87 are allowed to strike the strings 81. Due to the limited amount of available space above the hammer shanks 86 in a grand piano, the width A of the stop rail 84 cannot be very large. Therefore, the desired feel of the keys upon operating the keyboard cannot be realized.
If the stop rail is narrow, the cushioning member on the stop rail is largely deformed after repeated contact with the hammer shank. Therefore, the hammer striking movement cannot be securely prevented over time and the hammer striking sound may be accidentally produced. To solve the problem, the hammers can be strictly prevented from striking the strings by displacing the stop rail down toward the hammer shanks. However, this causes the feel of the keys upon operating the keyboard to vary significantly between the electronic performance mode and the normal piano performance mode.
Conventionally, to eliminate the difference in the feel of the keys between the modes, the stop rail is first set to its upper limit position, such that the stop rail can check the movement of the hammer shanks just before the hammers strike the strings. By adjusting the mechanical unit for thrusting the hammer shanks up in response to depression of the keys, the hammer strikes caused by deformation of the cushioning member are prevented. Although such countermeasures can eliminate the difference in the feel of keys upon operating the keyboard, the adjustment in the mechanical unit adversely affects the characteristic piano tone during the normal performance mode. Therefore, when the keyboard is operated in the normal piano performance mode, in which the strings are struck by hammers in response to depression of the keys, the feel of keys is badly influenced.
The problem with the provision of a conventional damper is that it impairs the delicate feel of the keys demanded by grand pianos.